The present invention relates to a module of electronic circuitry, in which an electronic circuit including a plurality of coils is formed on a magnetic circuit base plate, and more particularly, to an electronic circuit module with a plurality of coils wound on respective projections formed along one long side of a magnetic circuit base plate.
More specifically, although not limitative, the invention concerns a module, which is an integrated functional unit including an electronic circuit with coils, e.g., a DC-DC converter, and can be assembled as such in a different electronic apparatus.
An electronic circuit module is well known in the art, in which a magnetic plate of ferrite or the like is utilized as a circuit base plate and coils are mounted on portions of the base plate to make use of the magnetic properties of the base plate. There have been various proposals of the structure where coil elements such as transformers and inductors are formed. A typical one of such structures is disclosed in Japanese Utility Model Publication No. 59-45985 published Mar. 27, 1984.
In the disclosed technique, a magnetic circuit base plate is used, which is a rectangular magnetic plate with three or more pairs of notches formed along both the long sides such that the notches in each pair face each other, and the surface of which is formed with a circuit pattern, and coils are formed by winding wire in pair notches. The coils are connected to the circuit pattern such that they generate opposite polarity magnetic fields. Various circuit components are mounted on the magnetic circuit base plate, and a plurality of lead pins for connecting external circuits are mounted on an end portion of the magnetic circuit base plate.
With the electronic circuit module having the above construction, however, it is necessary to form notches along the opposite long sides of the magnetic circuit base plate. In addition, coils must be wound in every other pair of notches at the most in order to avoid magnetic interference between adjacent coils. Further, since each coil is formed in a pair of notches facing each other so that the base plate constitutes a core of the coil element, the operation of forming the coil is considerably cumbersome. Further, since the coils extend over the central portion of the base plate as well, not only the circuit component mounting area is reduced, but the circuit pattern design is significantly restricted. In case that a considerably large number of components are mounted as in the case of a DC-DC converter, it is necessary to increase the size of the base plate itself, and the base plate is liable to be broken or damaged due to a complicated shape.